driven through want to water, to find the prey on which it 

 feeds, will separate its toes whenever it strikes the water or 

 wishes to displace itself on its surface. The skin uniting 

 the base of the toes acquires, through the repeated separat- 

 ing of the toes, the habit of stretching; and in this way the 

 broad membrane between the toes of ducks and geese has 

 acquired the appearance we observe today." 



Darwin fell back occasionally upon Lamarck's doct- 

 rine in explanation of adaptation and of the origin of new 

 species, but included it only as a minor factor. The theory 

 of the action of use and disuse explains better than any 

 other (1) the origin of many indifferent characters such as 

 change of color-patterns of butterflies' wings due to changes 

 of temperature; (2) many simple adaptations of active 

 organs, such as the development of muscles and bone 

 crests; and (3) some simple adaptations of passive organs, 

 such as the loss of hair and the layer of fat in the skin of 

 whales. 



On the other hand Lamarckism does not explain satis- 

 factorily (1) many characters of active adaptation, such as 

 the penetration of the lung-sacs of birds into the bones; (2) 

 many complicated adaptations of active organs, such as 

 eyes, smelling organs, auditory organs, light-making organs; 

 and (3) all complicated passive adaptations such as mimi- 

 cry (Plate). 



According to Lamarck "the structure of organisms is 

 in harmony with the conditions under which they live; in 

 other words it is adapted to these conditions. The organ- 

 ism is shaped by the environment; usage develops the 

 organs; without usage they atrophy. The modifications 

 thus acquired are transmitted to posterity." 



Lamarckism as a scientific theory of evolution is in one 

 sense more complete than Darwinism in that it looks to the 

 very cause of the change of organisms by its method of 

 explaining adaptation. 



(d) — Darwin and Darwinism 



Charles Darwin (1809-1882)1 published his "Origin of 

 Species by Natural Selection'' in 1859 after twenty years of 

 most patient and painstaking labor. This work at once 

 compelled the attention of scientists by its wonderful com- 



(1) — Darwin was the grandson of Dr. Erasmus Darwin. He studied at 

 Edinburgli and Cambridge, then served as Naturalist on the ex- 

 ploring ship Beag-le (1831-1836). He settled at Downs in England 

 on his returr and began that wonderful series of researches on 

 plants and animals which he has described in a large number 

 of well written volumes. 



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